The invention concerns a device for clamping and centering of two parts which are to be welded together, such as, e.g., flange or edge against pipe, pipe to pipe, flared-out pipe against pipe, whereby the two parts can be welded together in the clamped position.
In machine construction and installations, the purpose of a device of the above-mentioned nature is to secure the spatial position of a workpiece, e.g., a pipe, against dislocation and turning, and to make it possible to partially or fully center it in a position where two end shapes fit against one another. For welding of the workpieces, the tension, centering and/or supply of shaping gas must be ascertained, as well as the intactness of the device.
In machine construction and installations, it is known how to accomplish the connection of rotationally non-symmetrical parts of pipeline installations, such as flange or edge against pipe, pipe to pipe, flared-out pipe against pipe, which will be referred to as welding parts in the following, namely in such a manner that the securing of the spatial position against dislocation or turning is achieved by means of stitching seams which are applied to the circumference of the parts to be connected and/or by means of welding tongs, vises or prisms.
In the case of such a connection, a number of different connectors and a considerable number of assembly personnel must be made available for producing the connection between the welding parts. This welded connection of, for instance, flange or edge against pipe, pipe to pipe, flared-out pipe to pipe, which has been produced with long production time and high production cost, will have different and varying quality of centering as well as of welding seam.
The width of the cylindrical turning device provided at the conical set-off, the diameter of which corresponds to the outside diameter of the pipe, is of particular importance of influencing the quality of the centering, e.g., in the case of connections of flange to pipe. Thus, for a pre-welding flange 50/75 DIN, i.e., nominal pre-welding width of 50 mm for an outside pipe diameter of 57 mm, the width of the set-off is approximately 8 mm. Bringing a pipe to a position flush with this setoff requires great manual skill and experience of the assembly crew, if the pipe is of a considerable length. Under practical circumstances, this task, e.g., a pre-welding flange of 50/57 DIN, which is to be welded to a rotationally non-symmetrical pipeline part with a length of 2.4 m, represents, in addition to new installations, a large percentage of all cases of repairs of pipeline installations as well as of assembly or connection of such installation portions at construction sites. The time required for orientation or centering is many times that required for pure welding/connection work. In addition to achieving this form-fitting centering for connection of the welding parts for pipelines and mountings, it is also necessary to arrange or align the screw holes in the flange in such a manner that they are symmetrical to the two main axes, this in order to achieve a symmetrical positioning of the holes. This requires additional effort in the centering.
Assuming constant welding performance, the quality of the welding connection is influenced by the centering of the welding parts in relation to one another and the uniform filling of the seam joint. If the centering is made by hand or by means of welding tongs, only insufficient form fitting of the welding parts and insufficiently uniform filling of the seam joints partially filled by stitch seams can be achieved.